【有上下界网络流】【ZOJ】2314 Reactor Cooling

【算法】有上下界网络流-无源汇(循环流)

【题解】http://www.cnblogs.com/onioncyc/p/6496532.html 

//未提交
#include<cstdio>
#include<algorithm>
#include<cstring>
using namespace std;
const int maxn=1000,maxm=100000,inf=0x3f3f3f3f;
struct edge{int from,v,flow;}e[maxm];
int S,T,TT,n,m,tot=1,first[maxn],cur[maxn],in[maxn],d[maxn],q[1010],lows[maxm];
void insert(int u,int v,int w)
{
tot++;e[tot].v=v;e[tot].flow=w;e[tot].from=first[u];first[u]=tot;
tot++;e[tot].v=u;e[tot].flow=0;e[tot].from=first[v];first[v]=tot;
}
bool bfs()
{
memset(d,-1,sizeof(d));
int head=0,tail=1;q[0]=S;d[S]=0;
while(head!=tail)
{
int x=q[head++];if(head>1000)head=0;
for(int i=first[x];i;i=e[i].from)
if(d[e[i].v]==-1&&e[i].flow)
{
d[e[i].v]=d[x]+1;
q[tail++]=e[i].v;
if(tail>1000)tail=0;
}
}
return d[T]!=-1;
}
int dfs(int x,int a)
{
if(x==T||a==0)return a;
int flow=0,f;
for(int& i=cur[x];i;i=e[i].from)
if(d[e[i].v]==d[x]+1&&(f=dfs(e[i].v,min(a,e[i].flow)))>0)
{
e[i].flow-=f;
e[i^1].flow+=f;
a-=f;
flow+=f;
if(a==0)break;
}
return flow;
}
int main()
{
scanf("%d",&TT);
while(TT--)
{
memset(first,0,sizeof(first));
memset(in,0,sizeof(in));
tot=1;
scanf("%d%d",&n,&m);
for(int i=1;i<=m;i++)
{
int u,v,w;
scanf("%d%d%d%d",&u,&v,&lows[i],&w);
in[u]-=lows[i];in[v]+=lows[i];
insert(u,v,w-lows[i]);
}
S=0,T=n+1;
for(int i=1;i<=n;i++)
{
if(in[i]>0)insert(S,i,in[i]);
if(in[i]<0)insert(i,T,-in[i]);
}
while(bfs())
{
for(int i=0;i<=n+1;i++)cur[i]=first[i];
dfs(S,inf);
}
bool ok=1;
for(int i=first[S];i;i=e[i].from)
if(e[i].flow)ok=0;
if(ok)
{
printf("YES\n");
for(int i=2;i<=m*2;i+=2)
printf("%d\n",e[i^1].flow+lows[i>>1]);
}
else printf("NO\n");
}
return 0;
}